Renovating french doors

I have a pair of external french doors, 2015 x 810, 40mm thick, pine with 2 glass panes inset in each. The timber framing in the doors is only about 100mm wide, so the doors are mostly glass, if you follow. They are currently each hung with 2 x 3 1/2" hinges.

They desperately needed paint and re-gluing, which I've done. As the original glass was only 3mm (4mm?), being 35 years old, I've replaced it with 6mm laminate. This has increased the weight of the doors, probably now about 15kg each (just a guess, certainly not as heavy as a solid door of the same size).

Questions:
1. Does this make the door heavy enough to require a third hinge?
2. If yes to q1, the middle of one of the pair of doors is bowed outwards by about 2mm, so how to fit a third hinge? Do you try and correct the bow, or simply fit the hinge to accommodate it?
3. How do you accurately line up the third hinge?

Just another weekend job!